Agricultural combines are large machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The residual crop material, or material other than grain, is discharged from the rear of the combine. Since the residual material includes dust and other small crop particulate, it is preferable to discharge the residual material away from the field of vision of the operator cab.
A harvesting platform is located at the front of the combine and harvests the crop. The harvested crop is directed to a feeder house for delivering the crop material to a crop processing assembly. The operator cab is generally positioned above the feeder house. The harvesting, conveying and processing of the crop material produces significant dust and small particle debris in the feeder house and processing assembly.
The crop material is threshed and separated into grain in the processing assembly. The crop processing assembly includes either a conventional transverse threshing cylinder and concave or a rotary threshing assembly. The rotary threshing assembly may be arranged axially or transversely. Another transverse rotating member, such as a feed beater or feed accelerator, usually assists movement of crop material from the feeder house into either the transverse or axial processing assembly.
A feed beater or accelerator is a rotating cylinder with transverse wings and controls the feeding of crop material into the crop processing assembly. A feed beater can be used with a transversely aligned conventional cylinder or with an axially or transversely aligned rotor. An undershot feed beater typically pulls the crop under the rotating beater using the transverse wings and pushes the crop into the inlet section of the crop processing assembly. As such, the returning wings, rotating along the top circumference of the beater, act as a fan and can push air back into the feeder house (i.e. forward relative to the rearward direction of movement of the crop material). This reverse or backward airflow can create turbulence or an airflow stall or air lock with the incoming airflow at the feeder house. These situations can cause the airflow in the feeder house to escape from the top or sides of the feeder house. The discharged air usually contains dust and small crop particulate from the harvesting process and, under certain operating conditions, can limit the field of vision from the operator cab.
In an effort to reduce feeder house dust from the operator cab field of vision, integral fans have been added to the feeder house to discharge air and dust out the sides or bottom of the feeder house. See for example the John Deere Air Flow system. Alternatively, an add-on attachment is available. See U.S. Pat. No. 6,036,600. In another alternatively, integral fans are added to the crop processing area to create additional airflow to pull the air and dust from the feeder house and through the combine. While these solutions may reduce dust, they also increase mechanical complexity, and thus cost and maintenance of combines and may reduce the power available for harvesting.